1. Field of the Invention
The present invention generally relates to the immobilization of nucleophilic initiators for curing thermosetting resins, such as mixed phenolic/epoxy thermosetting resins, directly on reinforcing fibers used to reinforce the matrix created from the thermosetting resins, as well as the creation of nucleophilic initiators on the surface of the reinforcing fibers. Specifically, the nucleophilic initiators are immobilized in a polymeric fiber coating or the fiber coating itself is the initiator.
2. Background Description
Fabrication processes for making fiber reinforced polymer matrix composites and fiber reinforced adhesives include a step whereby the fibers are brought into intimate contact with the resin. If the resin is a thermosetting material, the resin is desirably cured after the fibers and matrix are brought into contact. The resin must not cure prematurely, yet for many processes, rapid cures are desirable during composite formation. These two requirements are often conflicting. Oftentimes, if the initiator is added directly to the resin, premature cure occurs.
With novolac-epoxy resins, nucleophilic initiators for novolac-epoxy resins are normally nucleophiles such as tertiary phosphines or tertiary amines. Novolac-epoxy resins are relatively high viscosity resins and, as such, are currently processed from solution. Elevated temperatures in a resin "pre-fabrication bath" will be required for melt processes such as melt pregging, pultrusion, pressure injection, or filament winding. If sufficient initiator for resin cure is added to obtain rapid reaction during composite fabrication, premature curing in the resin pre-bath is a problem.